/*
Copyright 2021 The Matrix.org Foundation C.I.C.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import Recorder from "opus-recorder/dist/recorder.min.js";
import encoderPath from "opus-recorder/dist/encoderWorker.min.js";
import { SimpleObservable } from "matrix-widget-api";
import EventEmitter from "events";
import { logger } from "matrix-js-sdk/src/logger";

import MediaDeviceHandler from "../MediaDeviceHandler";
import { IDestroyable } from "../utils/IDestroyable";
import { Singleflight } from "../utils/Singleflight";
import { PayloadEvent, WORKLET_NAME } from "./consts";
import { UPDATE_EVENT } from "../stores/AsyncStore";
import { createAudioContext } from "./compat";
import { FixedRollingArray } from "../utils/FixedRollingArray";
import { clamp } from "../utils/numbers";
import recorderWorkletFactory from "./recorderWorkletFactory";

const CHANNELS = 1; // stereo isn't important
export const SAMPLE_RATE = 48000; // 48khz is what WebRTC uses. 12khz is where we lose quality.
const TARGET_MAX_LENGTH = 900; // 15 minutes in seconds. Somewhat arbitrary, though longer == larger files.
const TARGET_WARN_TIME_LEFT = 10; // 10 seconds, also somewhat arbitrary.

export const RECORDING_PLAYBACK_SAMPLES = 44;

interface RecorderOptions {
    bitrate: number;
    encoderApplication: number;
}

export const voiceRecorderOptions: RecorderOptions = {
    bitrate: 24000, // recommended Opus bitrate for high-quality VoIP
    encoderApplication: 2048, // voice
};

export const highQualityRecorderOptions: RecorderOptions = {
    bitrate: 96000, // recommended Opus bitrate for high-quality music/audio streaming
    encoderApplication: 2049, // full band audio
};

export interface IRecordingUpdate {
    waveform: number[]; // floating points between 0 (low) and 1 (high).
    timeSeconds: number; // float
}

export enum RecordingState {
    Started = "started",
    EndingSoon = "ending_soon", // emits an object with a single numerical value: secondsLeft
    Ended = "ended",
    Uploading = "uploading",
    Uploaded = "uploaded",
}

export class VoiceRecording extends EventEmitter implements IDestroyable {
    private recorder?: Recorder;
    private recorderContext?: AudioContext;
    private recorderSource?: MediaStreamAudioSourceNode;
    private recorderStream?: MediaStream;
    private recorderWorklet?: AudioWorkletNode;
    private recorderProcessor?: ScriptProcessorNode;
    private recording = false;
    private observable?: SimpleObservable<IRecordingUpdate>;
    private targetMaxLength: number | null = TARGET_MAX_LENGTH;
    public amplitudes: number[] = []; // at each second mark, generated
    private liveWaveform = new FixedRollingArray(RECORDING_PLAYBACK_SAMPLES, 0);
    public onDataAvailable?: (data: ArrayBuffer) => void;

    public get contentType(): string {
        return "audio/ogg";
    }

    public get durationSeconds(): number {
        if (!this.recorder || !this.recorderContext) throw new Error("Duration not available without a recording");
        return this.recorderContext.currentTime;
    }

    public get isRecording(): boolean {
        return this.recording;
    }

    public emit(event: string, ...args: any[]): boolean {
        super.emit(event, ...args);
        super.emit(UPDATE_EVENT, event, ...args);
        return true; // we don't ever care if the event had listeners, so just return "yes"
    }

    public disableMaxLength(): void {
        this.targetMaxLength = null;
    }

    private shouldRecordInHighQuality(): boolean {
        // Non-voice use case is suspected when noise suppression is disabled by the user.
        // When recording complex audio, higher quality is required to avoid audio artifacts.
        // This is a really arbitrary decision, but it can be refined/replaced at any time.
        return !MediaDeviceHandler.getAudioNoiseSuppression();
    }

    private async makeRecorder(): Promise<void> {
        try {
            this.recorderStream = await navigator.mediaDevices.getUserMedia({
                audio: {
                    channelCount: CHANNELS,
                    deviceId: MediaDeviceHandler.getAudioInput(),
                    autoGainControl: { ideal: MediaDeviceHandler.getAudioAutoGainControl() },
                    echoCancellation: { ideal: MediaDeviceHandler.getAudioEchoCancellation() },
                    noiseSuppression: { ideal: MediaDeviceHandler.getAudioNoiseSuppression() },
                },
            });
            this.recorderContext = createAudioContext({
                // latencyHint: "interactive", // we don't want a latency hint (this causes data smoothing)
            });
            this.recorderSource = this.recorderContext.createMediaStreamSource(this.recorderStream);

            // Connect our inputs and outputs
            if (this.recorderContext.audioWorklet) {
                // Set up our worklet. We use this for timing information and waveform analysis: the
                // web audio API prefers this be done async to avoid holding the main thread with math.
                await recorderWorkletFactory(this.recorderContext);

                this.recorderWorklet = new AudioWorkletNode(this.recorderContext, WORKLET_NAME);
                this.recorderSource.connect(this.recorderWorklet);
                this.recorderWorklet.connect(this.recorderContext.destination);

                // Dev note: we can't use `addEventListener` for some reason. It just doesn't work.
                this.recorderWorklet.port.onmessage = (ev) => {
                    switch (ev.data["ev"]) {
                        case PayloadEvent.Timekeep:
                            this.processAudioUpdate(ev.data["timeSeconds"]);
                            break;
                        case PayloadEvent.AmplitudeMark:
                            // Sanity check to make sure we're adding about one sample per second
                            if (ev.data["forIndex"] === this.amplitudes.length) {
                                this.amplitudes.push(ev.data["amplitude"]);
                                this.liveWaveform.pushValue(ev.data["amplitude"]);
                            }
                            break;
                    }
                };
            } else {
                // Safari fallback: use a processor node instead, buffered to 1024 bytes of data
                // like the worklet is.
                this.recorderProcessor = this.recorderContext.createScriptProcessor(1024, CHANNELS, CHANNELS);
                this.recorderSource.connect(this.recorderProcessor);
                this.recorderProcessor.connect(this.recorderContext.destination);
                this.recorderProcessor.addEventListener("audioprocess", this.onAudioProcess);
            }

            const recorderOptions = this.shouldRecordInHighQuality()
                ? highQualityRecorderOptions
                : voiceRecorderOptions;
            const { encoderApplication, bitrate } = recorderOptions;

            this.recorder = new Recorder({
                encoderPath, // magic from webpack
                encoderSampleRate: SAMPLE_RATE,
                encoderApplication: encoderApplication,
                streamPages: true, // this speeds up the encoding process by using CPU over time
                encoderFrameSize: 20, // ms, arbitrary frame size we send to the encoder
                numberOfChannels: CHANNELS,
                sourceNode: this.recorderSource,
                encoderBitRate: bitrate,

                // We use low values for the following to ease CPU usage - the resulting waveform
                // is indistinguishable for a voice message. Note that the underlying library will
                // pick defaults which prefer the highest possible quality, CPU be damned.
                encoderComplexity: 3, // 0-10, 10 is slow and high quality.
                resampleQuality: 3, // 0-10, 10 is slow and high quality
            });

            // not using EventEmitter here because it leads to detached bufferes
            this.recorder.ondataavailable = (data: ArrayBuffer) => this.onDataAvailable?.(data);
        } catch (e) {
            logger.error("Error starting recording: ", e);
            if (e instanceof DOMException) {
                // Unhelpful DOMExceptions are common - parse them sanely
                logger.error(`${e.name} (${e.code}): ${e.message}`);
            }

            // Clean up as best as possible
            if (this.recorderStream) this.recorderStream.getTracks().forEach((t) => t.stop());
            if (this.recorderSource) this.recorderSource.disconnect();
            if (this.recorder) this.recorder.close();
            if (this.recorderContext) {
                // noinspection ES6MissingAwait - not important that we wait
                this.recorderContext.close();
            }

            throw e; // rethrow so upstream can handle it
        }
    }

    public get liveData(): SimpleObservable<IRecordingUpdate> {
        if (!this.recording || !this.observable) throw new Error("No observable when not recording");
        return this.observable;
    }

    public get isSupported(): boolean {
        return !!Recorder.isRecordingSupported();
    }

    private onAudioProcess = (ev: AudioProcessingEvent): void => {
        this.processAudioUpdate(ev.playbackTime);

        // We skip the functionality of the worklet regarding waveform calculations: we
        // should get that information pretty quick during the playback info.
    };

    private processAudioUpdate = (timeSeconds: number): void => {
        if (!this.recording) return;

        this.observable!.update({
            waveform: this.liveWaveform.value.map((v) => clamp(v, 0, 1)),
            timeSeconds: timeSeconds,
        });

        // Now that we've updated the data/waveform, let's do a time check. We don't want to
        // go horribly over the limit. We also emit a warning state if needed.
        //
        // We use the recorder's perspective of time to make sure we don't cut off the last
        // frame of audio, otherwise we end up with a 14:59 clip (899.68 seconds). This extra
        // safety can allow us to overshoot the target a bit, but at least when we say 15min
        // maximum we actually mean it.
        //
        // In testing, recorder time and worker time lag by about 400ms, which is roughly the
        // time needed to encode a sample/frame.
        //

        if (!this.targetMaxLength) {
            // skip time checks if max length has been disabled
            return;
        }

        const secondsLeft = TARGET_MAX_LENGTH - this.recorderSeconds!;
        if (secondsLeft < 0) {
            // go over to make sure we definitely capture that last frame
            // noinspection JSIgnoredPromiseFromCall - we aren't concerned with it overlapping
            this.stop();
        } else if (secondsLeft <= TARGET_WARN_TIME_LEFT) {
            Singleflight.for(this, "ending_soon").do(() => {
                this.emit(RecordingState.EndingSoon, { secondsLeft });
                return Singleflight.Void;
            });
        }
    };

    /**
     * {@link https://github.com/chris-rudmin/opus-recorder#instance-fields ref for recorderSeconds}
     */
    public get recorderSeconds(): number | undefined {
        if (!this.recorder) return undefined;
        return this.recorder.encodedSamplePosition / 48000;
    }

    public async start(): Promise<void> {
        if (this.recording) {
            throw new Error("Recording already in progress");
        }
        if (this.observable) {
            this.observable.close();
        }
        this.observable = new SimpleObservable<IRecordingUpdate>();
        await this.makeRecorder();
        await this.recorder?.start();
        this.recording = true;
        this.emit(RecordingState.Started);
    }

    public async stop(): Promise<void> {
        return Singleflight.for(this, "stop").do(async (): Promise<void> => {
            if (!this.recording) {
                throw new Error("No recording to stop");
            }

            // Disconnect the source early to start shutting down resources
            await this.recorder!.stop(); // stop first to flush the last frame
            this.recorderSource!.disconnect();
            if (this.recorderWorklet) this.recorderWorklet.disconnect();
            if (this.recorderProcessor) {
                this.recorderProcessor.disconnect();
                this.recorderProcessor.removeEventListener("audioprocess", this.onAudioProcess);
            }

            // close the context after the recorder so the recorder doesn't try to
            // connect anything to the context (this would generate a warning)
            await this.recorderContext!.close();

            // Now stop all the media tracks so we can release them back to the user/OS
            this.recorderStream!.getTracks().forEach((t) => t.stop());

            // Finally do our post-processing and clean up
            this.recording = false;
            await this.recorder!.close();
            this.emit(RecordingState.Ended);
        });
    }

    public destroy(): void {
        // noinspection JSIgnoredPromiseFromCall - not concerned about stop() being called async here
        this.stop();
        this.removeAllListeners();
        this.onDataAvailable = undefined;
        Singleflight.forgetAllFor(this);
        // noinspection JSIgnoredPromiseFromCall - not concerned about being called async here
        this.observable?.close();
    }
}
